Charles VIII of Sweden (in reality Charles II), Charles I of Norway, also Carl (Swedish: Karl Knutsson), was king of Sweden (1448–1457, 1464–1465 and from 1467 to his death in 1470) and king of Norway (1449–1450).

At the death of Christopher in 1448, without a direct heir, Charles was elected king of Sweden on 20 June and on 28 June he was hailed as the new monarch at the Stones of Mora, not far from Uppsala, mostly due to his own military troops being present at the place, against the wishes of regents Bengt and Nils Jönsson (Oxenstierna). The Danish had in September 1448 elected Christian I as their new monarch. A rivalry ensued between Charles and Christian for the throne of Norway, which had also been ruled by Christopher, with both kings gaining support from various factions in the Norwegian Council of the realm. In 1449 a portion of the Norwegian council elected Charles King of Norway, and he was crowned in Nidaros Cathedral in Trondheim on 20 November. However, Christian also continued pursuing his claim to Norway. The Swedish aristocracy was reluctant to back Charles in a war against Denmark over Norway, and already in 1450, Charles was forced to relinquish the throne of Norway in favour of Christian.

From 1451, Sweden and Denmark were in state of war against each other. Because of devastating warring, a growing opposition against Charles emerged among the nobility in Sweden. The strongest opponent was the Swedish church which opposed Charles's efforts to concentrate royal and secular power. Other opponents were the family group of Oxenstierna and the House of Vasa, which had been on the opposing side in the election of king and lost.

During the next 20 years, Charles was deposed twice, only to regain the throne and reign three times (1448–57, 1464–65, 1467–70).

In 1457, a rebellion took place, led by Archbishop Jöns Bengtsson (Oxenstierna) and a nobleman, Erik Axelsson Tott. Charles went into exile to Danzig (Gdańsk). The two leaders of the revolt took the regentship, and organized the election of Christian I of Denmark as king (firstly in Turku, then in Stockholm).

In 1463, King Christian quarrelled with the Archbishop because of his taxation policies. The Archbishop was imprisoned, which resulted in a rebellion by his relatives, and led to Christian being driven out of Sweden. Charles was recalled by the rebels and returned at the head of a force of German and Polish mercenaries. Upon arrival in Sweden he found himself at war with the Archbishop and after two bloody battles in the winter of 1464–1465 Charles was again exiled. In 1467, the regent Erik Axelsson Tott, now having reverted to support Charles, once more had him crowned. Charles then reigned for three years, sharing power with the Riksråd, until his death in Stockholm in May 1470.